This proposal addresses a gap in knowledge about how Attention Deficit Hyperactivity Disorder may act as a catalyst in the development of Conduct Disorder. In 1987-88, a sample was formed at two sites, of 177 prepubertal outpatient boys, most of whom had been referred for attention deficit-hyperactivity and/or conduct problems. These boys have currently completed the second of three planned annual assessments. This proposal aims to follow up the boys into adolescence with an additional four annual assessments. Those diagnosed as having Attention Deficit Hyperactivity Disorder (ADHD) and Conduct Disorder (CD) (compared to boys with CD only, with ADHD only, or with neither disorder) are thought to be particularly at risk for early onset, greater variety, greater persistence, and greater seriousness of delinquent behavior, and probably are more likely to engage in substance abuse and high-risk sexual behavior. Also, ADHD boys without prepubertal CD, compared to controls, are thought to be at risk for late- onset CD and subsequent substance use and possibly high-risk sexual behavior. In addition, CD and ADHD may increase the risk for later depression and comorbid CD and depression may influence the course of CD and the risk for suicidal behavior. The proposed study aims at elucidating the emergence of these deviant outcomes, and relating the outcomes to the presence of several risk factors in addition to CD and ADHD, such as antisocial personality in parents, psychopathology in family members, poor parenting, peer influences, the boy's intelligence and academic performance, and so on. The study will also allow for an evaluation of the long-term predictive utility of different symptoms and diagnostic criteria (DSM-III-R and possible alternatives) for the classification of disruptive behavior disorders in childhood and adolescence.